Gravel content effect on site response of sand-like gravelly soil deposits by centrifuge model tests

The sand-like gravelly soils are more prone to suffer from liquefaction disasters than those with gravel-like features and cause comparable liquefaction phenomena to sands. However, the gravel content effect on site response of such soil deposits was poorly understood. In this study, three dynamic centrifuge model tests with gravel contents of 0, 20 %, and 60 % were conducted under the same equivalent skeleton void ratio, which aims to reveal the gravel content effect on site response from small to large shear strains. The test results show that the ground stiffness increases with the increase of gravel content, which in turn leads to the increase of site natural frequency and the decrease of acceleration amplification factor. The gravel content effect is not evident under small sine wave motion, and the GC60 model ground exhibits the poorest liquefaction susceptibility. On the contrary, the gravel content effect is sufficiently mobilized to maintain the skeleton stability of sand-gravel mixtures under large sine wave motion, and the GC60 model ground shows the best liquefaction performance. For submerged and homogeneous gravelly soil deposits, the gravel content effect on site classification and the related seismic design parameters is significant. However, the overestimation of the site classification due to the gravel content effect on soil stiffness is unsafe for gravelly soil deposits with high gravel contents when the seismic intensity is low. Therefore, obtaining suitable and economical seismic design parameters for superstructures built on gravelly soil sites deserves further study.